In the art of water beds, blanket-type electric resistance heaters are provided to heat and maintain the water in flotation mattresses at desired and comfortable temperature. The heaters are arranged in flat engagement between the flat mattress supporting platforms of the water bed frames and the bottom walls of the water filled, bladder-like flotation mattresses. Control means are provided to adjust and set the temperature to be maintained in the mattresses. The control means include box-like control units with manually operable temperature adjusting knobs arranged at the exterior of the beds and connected with the heaters by elongate flexible power cords and with power service outlets, remote from the beds, by elongate flexible service cords. In addition to the above, the control units are provided with small temperature sensing devices, such as thermocouples or thermosters at the free ends of thin, elongate, flexible conductors. The conductors extend from the control units between their related bed platforms and mattresses to arrange the temperature sensing devices at their ends in heat conducting contact with the mattresses, in effective operating spaced relationship from the heaters and the sides of the bed structures.
The above noted control units include suitable switching circuits which operate to turn the flow of current through the heaters on and off in response to the temperature sensed by the temperature sensing devices, whereby the heaters operate continuously until the temperature of their related mattresses reach set temperatures and are thereafter turned on and off to maintain the temperature of the mattresses at said set temperature.
While the above type of water bed heaters and control means therefore have proven to be reasonably satisfactory, a notable and serious problem which is often encountered is the misplacement and/or displacement of the temperature sensing devices which result in the failure and/or inability of the control means to operate as intended.
For example, it is not infrequent that the temperature sensing devices occur adjacent to or in excessively close proximity to the heaters with the result that the devices operate in response to the temperature of the heaters, rather than to the temperature of the mattresses. When this occurs, the heaters are turned off before the mattresses can be brought up to set temperature.
In other instances, the sensing devices occur in air pockets defined by and between the mattresses and their related platforms. As a result, desired heat conducting contact between the devices and the mattresses is not established and the heaters are turned on and caused to operate for excessive periods of time. This results in overheating the mattresses and/or cause other serious and irreparable damage.
In both of the examples given above, the sensing devices are either misplaced during assembly of the beds and installation of the heaters and sensing devices or the devices are pulled or otherwise caused to move out of proper set position by normal working of the beds, over protracted periods of time. More often than not, improper installation is a cause.
Improper installation of the heaters and of the temperature sensing devices in water bed structures is generally the result of the inability of the purchasers and "do it yourself" installers of the heaters and their control means to understand and/or follow the simplest of printed installation instructions which are commonly provided with water beds and water bed heating means.
Adding to the above is the fact that the separate elongate flexible power cords extending from the heaters to the control units and the elongate flexible conductors extending from the temperature sensing devices to the control units are oftentimes difficult to manipulate and frequently become adversely twisted and tangled during and before installation can be completed, with the result that relative placement of the heaters and sensing devices is not readily determinable.
It should be noted that very few people understand and appreciate the reasons for and the importance of properly installing the heat sensing devices of water bed heater control means and that the overwhelming majority of persons who buy and install water bed heating means are without that special knowledge and background which would enable them to understand the best of installation instructions with sufficient certainty to knowingly effect proper assembly and/or installation of the equipment involved.
In addition to the above, and possibly a more serious problem found to exist in the common installation of water bed heaters and control means therefore resides in the fact that during normal use and working of the beds, the heaters and temperature sensing devices tend to move or migrate between the bed platforms and mattresses and are subject to being adversely displaced. Such movement and/or displacement of parts can result from intermittent, inadvertent, tugging or pulling of portions of the power cords and conductors occurring at the exterior of the beds and/or can be caused by those wave or surge generated forces which are transmitted through and between the mattresses and the platforms, and thus onto and through the portions of the cores and conductors extending between the mattresses and platforms. While the flat blanket-type heaters (having great surface areas) are not frequently caused to move and become displaced in the manner set forth above, the small temperature sensing devices and their related flexible conductors are highly susceptible to being moved and displaced under the above noted conditions and/or circumstances.
In addition to the foregoing, the fact that the power cords for the heaters and the conductors for the temperature sensing devices are separate or independent from each other compounds the likelihood that a cord or conductor will be inadvertently engaged, at the exterior of the bed structure, and subjected to forces which are likely to displace structure, as noted in the preceding or cause other adverse effects.